We propose to study the mechanism of secretion of periplasmic proteins in Escherichia coli, focusing on the possible specificity of the protein secretion channels. To do this, we first use an immunological approach (crossed immunoelectrophoresis) to identify large number of periplasmic proteins (and by implication, th genes encoding them). These proteins will then be screened to identify those whose secretion is not affected by the known mutations of the protein secretation apparatus (see-mutants). Once such proteins are identified, we will attempt to isolate corresponding sec mutants that affect the secretion of such proteins. These novel sec mutants may define an alternative pathway of protein secretion. In addition a plasmid "pool" for periplasmic protein coding-genes will be constructured, using the antibodies directed against periplasmic proteins. The availability of such a plasmic pool should help pursuing the project. In order to study further the basis of specificity of protein localization channels, gene fusions coding hybrid proteins composed of the signal sequence of phoA (encoding alkaline phosphatase) and the structural part of non-periplsmic protein will be constructed. This will entail using a previously constructed "fusion vector" and should help show what parts of protein determines final cellular localization and pathway of secretion. This approach will further be extended by construction of a special kind of ord (open rading frame) vector that allow the examination of the compatibility of polypeptide chain coded by any open reading frame with the secretion apparatus engaged in alkaline phosphatase secretion.